1. Field of the Invention: This invention relates to the art of gas-fired hot water heaters and, particularly, to means for extracting more heat from the central flue pipe before the heat goes up the stack and returns to the atmosphere.
2. Description of the Prior Art: The Rouet et al U.S. Pat. No. 3,580,224 describes a gas hot water heater having a small central pilot flue that is surrounded by a central tank, and it, in turn, is surrounded by an annular flue that is defined between the central tank and the outer tank. The cold water supply pipe discharges into the bottom of the outer tank.
The Fuller U.S. Pat. No. 1,552,292 describes a gas hot water heater having an attachment or percolator that is designed to improve circulation, and it includes a tubular portion that is open at both ends and surrounds the central vertical flue. The cold water intake pipe discharges cold water over the perforated flange fitted over the lower dome that is, in turn, positioned over the gas burner. The circulation of water is then through the holes in the perforated lower flange, and then up through the annular chamber that surrounds the central vertical flue. The hot water spills out over the top edge of this concentric tube.
The Dobias U.S. Pat. No. 4,474,139 describes either a gas or an electric hot water heater that includes a water tank having a jacket which rapidly absorbs heat from and gives up heat to the water, which jacket is an energy saver for the water heater. The jacket is constructed of eight, separate, corrugated cylinders. There is a central pipe extending down through the length thereof. These corrugated cylinders are provided with a large plurality of small openings to render these cylinders porous so that the water will pass therethrough in a somewhat restricted manner.
The Meacham U.S. Pat. No. 1,101,872 describes a small hot water heater having inner and outer shelves that can be readily separated so that the scale deposit from the water can be readily removed from the walls of the inner and outer shelves. The inner casing is corrugated horizontally to form a larger heating surface, thus increasing the heating capacity. The cold water supply pipe is in the lower portion of the heater.
The Syler U.S. Pat. No. 4,505,231 describes a gas hot water heater with sediment removal means. There is a central vertical flue that is vented to the atmosphere. There is an inlet agitator tube that is mounted through the top wall of the tank and extends vertically downward and terminates in a semicircular curved portion that lies in a substantially horizontal plane slightly spaced above the bottom dome. This semicircular curved portion is fitted with a series of inclined openings for directing streams of water against the top surface of the bottom dome each time water is drawn out of the top of the tank. These streams of water serve to agitate the water in the bottom of the tank to prevent the accumulation of sediment therein.
The Epling et al U.S. Pat. No. 2,561,465 describes a water tank having a central vertical flue. In the bottom portion of the tank is a circular deflector plate through which the flue pipe extends. This deflector plate is inclined, and it is provided with diametrically opposed, semicircular cutouts. There is a semicircular hot water tube fastened to the inner surface of the tank and in alignment with the cutout. Several of the modifications of this patent do not employ a flue tube.
The Harris U.S. Pat. No. 1,971,139 describes a gas hot water heater having a central vertical flue. There is a water tube surrounding the vertical flue, and there is also an inert water space within the water tube. Service water is supplied to the service water space by a long vertical pipe that empties near the bottom of the tank. The vented inert water tube that surrounds the vertical flue, and the water head at the bottom of the service water space, which parallels the dome that overlies the gas burner both constitute an indirect heat transfer wall. A circular partition is placed in the inert water space for the purpose of directing circulation by convection upwardly along the outer surface of the vertical flue and downwardly along the inner surface of the water tube. There is an external controller having three separate assemblies; namely, a water valve, a safety valve, and a central cavity that is connected to the inert water space by a horizontal water pipe. However, the inert water tube is not frequently contaminated by infusisons of service water.
The last patent is to Mac Cracken et al U.S. Pat. No. 2,773,488, which describes a boiler-burner unit, where water is brought into the outer jacket from a circulating pump through a curved T-fitting. There is a high velocity burner mounted at the top of the insulated cover. The boiler is made up of two, similar, coaxially arranged envelope sections, where one is disposed within the other.